Not Applicable
Not Applicable
1. Field of the Invention
This invention relates to markers and labels for electronic article surveillance (EAS) systems, and more particularly to manufacturing methods for magnetomechanical and magnetoacoustic EAS markers and labels using RF molding and deposition.
2. Description of the Related Art
U.S. Pat. No. 4,510,489, the ""489 patent, discloses an EAS marker made of an elongated strip of magnetostrictive ferromagnetic material disposed adjacent to a ferromagnetic element that, when magnetized, magnetically biases the strip and arms it to resonate mechanically at a preselected resonant frequency. The marker resonates when subjected to an interrogation field at a frequency at or near the marker""s resonant frequency. The response of the marker at the marker""s resonant frequency can be detected by EAS receiving equipment, thus providing an electronic marker for use in EAS systems. As used herein, the term xe2x80x9cmarkerxe2x80x9d refers to, and is used interchangeably with, markers, labels, and tags used to trigger EAS systems.
The marker of the ""489 patent is constructed of a resonator, an elongated ductile strip of magnetostrictive ferromagnetic material disposed adjacent a ferromagnetic element. The ferromagnetic element is a high coercivity biasing magnet that, when magnetized, is capable of applying a DC magnetic bias field to the resonator. The resonator is placed within a hollow recess or cavity of the marker housing with the bias held in an adjacent plane parallel to the resonator so that the bias does not cause mechanical interference with the vibration of the resonator. Because the resonator must vibrate freely within its cavity and the bias is maintained in a parallel adjacent plane, the marker has a required minimum thickness to accommodate the adjacent parallel planes and permit free vibration of the resonator.
Presently, the EAS markers described above are manufactured using a vacuum thermal forming process. Referring to FIG. 1, the resonator cavity 2 is formed from a flat planar plastic material 3, and results in a flange 4 extending around the cavity perimeter to which the lid material 5 is thermo-sealed. The lid 5 tends to sag toward the cavity 2, and the label 1 has a tendency to bow due to shrinkage in the polymer laminates 6 during the thermo-sealing process effectively reducing the depth of the cavity 2. The resonator cavity 2 must be made deeper to compensate for this cavity depth reduction to permit mechanical freedom for the resonator 7. Since the thermo-formed cavity 2 essentially rises out of the plane of its flanges 4, it can be crushed by applied pressure such as by stacking merchandise or vandalism. Crushing the resonator cavity 2 prevents the resonator 7 from freely moving when resonating. The quality of the cavity formation can be improved.
In addition, there are EAS marker applications in which a flat marker is desired. A flat EAS marker is defined herein as an EAS marker of lower minimum thickness than is required to accommodate a bias and a resonator that are maintained in stacked parallel adjacent planes as described above. A flat marker can provide a larger surface area for the attachment of indicia, and may be more bendable. U.S. patent application Ser. No. 09/584,559, the ""559 application, assigned to Sensormatic Electronics Corporation, discloses a xe2x80x9cside-by-sidexe2x80x9d bias configuration that results in flat magnetomechanical EAS marker. The disclosure of the ""559 application is incorporated herein by reference in its entirety. The ""559 application includes disclosure of manufacturing methods for flat EAS markers. Improved manufacturing methods are desired.
A first aspect of the invention is a method of making a magnetomechanical electronic article surveillance marker that includes deposition of at least one elongated bias magnet onto a substrate, depositing a cavity layer onto the substrate where the cavity layer defines an elongated cavity adjacent the bias magnet. Placing a magnetomechanical resonator into the cavity and sealing a cover onto the cavity layer wherein the resonator is captured in the cavity and free to mechanically vibrate substantially unencumbered.
Further, two elongated bias magnets can be deposited on the substrate layer in parallel relation to each other, the elongated cavity can be defined between the two elongated bias magnets. A resonator support member can be deposited in the cavity that rests against a mechanical vibration nodal point of the resonator when the resonator is disposed in the cavity to support the resonator without substantially encumbering mechanical vibration thereof. The elongated bias magnet and the cavity layer can be deposited on opposite sides of the substrate. A first portion of the cavity layer can be deposited on the substrate and a second portion of the cavity layer can be deposited on the cover where sealing connects the first and second cavity layer portions together defining the cavity so the cavity is substantially impervious to restricting the resonator. An adhesive layer can be deposited on the cavity layer prior to sealing a cover onto the cavity layer.
A second aspect of the invention is a method of making a magnetomechanical electronic article surveillance marker that includes placing at least one elongated bias magnet on a substrate layer, depositing a cavity layer on the substrate that covers and attaches the bias magnet to the substrate and defines an elongated cavity adjacent the bias magnet. Placing a magnetomechanical resonator in the cavity and sealing a cover onto the cavity layer where the resonator is captured in the cavity and free to mechanically vibrate unencumbered.
Further, two elongated bias magnets can be placed on the substrate layer in parallel relation to each other with the elongated cavity defined between the two elongated bias magnets. A resonator support member can be deposited in the cavity to rest against a mechanical vibration nodal point of the resonator when the resonator is disposed in the cavity thereby supporting the resonator without substantially encumbering mechanical vibration thereof. A first portion of the cavity layer is deposited on the substrate and a second portion of said cavity layer is deposited on the cover where sealing connects the first and second cavity layer portions together defining the cavity where the cavity is substantially impervious to restricting the resonator. An adhesive layer can be deposited on the cavity layer prior to sealing a cover onto the cavity layer.
A third aspect of the invention is a method of making a magnetomechanical electronic article surveillance marker that includes depositing a cavity layer on a magnetizable substrate layer, the cavity layer defining an elongated cavity. A resonator support member can be deposited in the cavity. Placing a magnetomechanical resonator in the cavity, the resonator support member being disposed between the resonator and the magnetizable substrate layer, and sealing a cover onto the cavity layer wherein the resonator is captured in the cavity and free to mechanically vibrate unencumbered.
Further, the resonator support member is adapted to rest against a mechanical vibration nodal point of the magnetomechanical resonator when the resonator is disposed in the cavity thereby supporting the resonator without substantially encumbering mechanical vibration thereof.
A fourth aspect of the invention is a method of making a magnetomechanical electronic article surveillance marker including molding a cavity in a plastic substrate, the cavity sized to receive a magnetomechanical resonator, the substrate sized relatively slightly larger than the magnetomechanical resonator. Placing the magnetomechanical resonator into the cavity and sealing a first cover layer to the plastic substrate wherein the resonator is captured in the cavity and free to mechanically vibrate unencumbered, the first cover layer being sized larger than the plastic substrate. Placing at least one bias magnet on the first cover layer adjacent the plastic substrate and sealing a second cover layer to the plastic substrate, to the bias magnet, and to the first cover layer, where the bias magnet is held substantially fixed in position relative to the resonator.
Further, the second cover layer can be an adhesive layer. Two bias magnets are placed on the first cover layer, the plastic substrate disposed adjacent and between the bias magnets, and the second cover layer sealing both of the bias magnets in a position substantially fixed relative to the resonator. The cavity is molded using RF molding.
A fifth aspect of the invention is a method of making a magnetomechanical electronic article surveillance marker including placing at least one bias magnet on a plastic substrate, and molding a cavity in the plastic substrate adjacent the bias magnet. The cavity sized to receive a magnetomechanical resonator, the bias magnet being embedded into the plastic substrate substantially simultaneously with the cavity formation. Placing a magnetomechanical resonator into the cavity and sealing a cover layer to the plastic substrate where the resonator is captured in the cavity and free to mechanically vibrate unencumbered.
Further, two bias magnets are placed on the plastic substrate and the cavity is molded between the bias magnets, both of the bias magnets can be embedded into the plastic substrate. A resonator support member can be molded into the cavity wherein the resonator support member is adapted to rest against a mechanical vibration nodal point of the resonator when the resonator is disposed in the cavity thereby supporting the resonator without substantially encumbering mechanical vibration thereof. The cavity is molded using RF molding.
A sixth aspect of the invention is a method of making a magnetomechanical electronic article surveillance marker including molding a resonator cavity and a bias cavity in a plastic substrate using RF molding. The resonator cavity is sized to receive a magnetomechanical resonator, the bias cavity sized to receive a bias magnet. Placing a magnetomechanical resonator into the resonator cavity, and placing a bias magnet into the bias cavity, and sealing a cover layer to the plastic substrate where the resonator is captured in the cavity and free to mechanically vibrate unencumbered and the bias magnet is retained in a substantially fixed position.
Further, molding includes molding two bias cavities and a bias magnet is placed in each bias cavity, each bias magnet being retained in a substantially fixed position by the cover layer. The cover layer can be sealed to the plastic substrate using ultrasound.
Objectives, advantages, and applications of the present invention will be made apparent by the following detailed description of the preferred embodiments of the invention.